2,815 research outputs found
The ASL-CDI 2.0: an updated, normed adaptation of the MacArthur Bates Communicative Development Inventory for American Sign Language
Vocabulary is a critical early marker of language development. The MacArthur Bates Communicative Development Inventory has been adapted to dozens of languages, and provides a bird’s-eye view of children’s early vocabularies which can be informative for both research and clinical purposes. We present an update to the American Sign Language Communicative Development Inventory (the ASL-CDI 2.0, https://www.aslcdi.org), a normed assessment of early ASL vocabulary that can be widely administered online by individuals with no formal training in sign language linguistics. The ASL-CDI 2.0 includes receptive and expressive vocabulary, and a Gestures and Phrases section; it also introduces an online interface that presents ASL signs as videos. We validated the ASL-CDI 2.0 with expressive and receptive in-person tasks administered to a subset of participants. The norming sample presented here consists of 120 deaf children (ages 9 to 73 months) with deaf parents. We present an analysis of the measurement properties of the ASL-CDI 2.0. Vocabulary increases with age, as expected. We see an early noun bias that shifts with age, and a lag between receptive and expressive vocabulary. We present these findings with indications for how the ASL-CDI 2.0 may be used in a range of clinical and research settingsAccepted manuscrip
Communicative and linguistic development in preterm children: a longitudinal study from 12 to 24 months.
BACKGROUND: Research conducted on preterm children's linguistic skills has provided varying pictures, and the question of whether and to what extent preterm children are delayed in early language acquisition remains largely unresolved. AIMS: To examine communicative and linguistic development during the second year in a group of Italian children born prematurely using the 'Primo Vocabolario del Bambino' (PVB), the Italian version of the MacArthur-Bates Communicative Development Inventory. The primary goal was to compare action/gesture production, word comprehension, and word production, and the relationship between these three domains in preterm children and to normative data obtained from a large sample of Italian children born at term. A second aim was to address the longstanding debate regarding the use of chronological versus corrected gestational age in the assessment of preterm children's abilities. METHODS & PROCEDURES: Parents of twelve preterm children completed the PVB questionnaire at five age points during the children's second year, and scores were compared with those from a normative sample of full-term children and those of 59 full-term children selected as a control group from the normative sample for the PVB. OUTCOMES & RESULTS: Preterm children exhibited a delay in all three aspects of communication and language. In particular, communicative-linguistic age tended to lag approximately 3 months behind chronological age when children were between the ages of 12 and 24 months. When chronological age was used, preterm children's percentile scores for all three components of communication and language fell within the lower limits of the normal range, while scores calculated using corrected age either fell at or above the 50th percentile. CONCLUSIONS & IMPLICATIONS: Findings suggest that despite the significant biological risk engendered by premature birth, early communicative and linguistic development appears to proceed in a relatively robust fashion among preterm children, with tight relations across communicative domains as in full-term children. Employing both chronological and corrected gestational age criteria in the evaluation of preterm children's abilities may provide important information about their progress in language acquisition. This may be especially important during the initial stages of communicative and linguistic development, inasmuch as comparisons of the two sets of scores may provide clinicians with a way to distinguish children who may be at risk for language problems from those who may be expected to progress normally
Estimation and reduction of the uncertainties in chemical models: Application to hot core chemistry
It is not common to consider the role of uncertainties in the rate
coefficients used in interstellar gas-phase chemical models. In this paper, we
report a new method to determine both the uncertainties in calculated molecular
abundances and their sensitivities to underlying uncertainties in the kinetic
data utilized. The method is used in hot core models to determine if previous
analyses of the age and the applicable cosmic-ray ionization rate are valid. We
conclude that for young hot cores ( yr), the modeling uncertainties
related to rate coefficients are reasonable so that comparisons with
observations make sense. On the contrary, the modeling of older hot cores is
characterized by strong uncertainties for some of the important species. In
both cases, it is crucial to take into account these uncertainties to draw
conclusions from the comparison of observations with chemical models.Comment: Accepted for publication in A&
Kinematics of dense gas in the L1495 filament
We study the kinematics of the dense gas of starless and protostellar cores
traced by the N2D+(2-1), N2H+(1-0), DCO+(2-1), and H13CO+(1-0) transitions
along the L1495 filament and the kinematic links between the cores and the
surrounding molecular cloud.
We measure velocity dispersions, local and total velocity gradients and
estimate the specific angular momenta of 13 dense cores in the four transitions
using the on-the-fly observations with the IRAM 30 m antenna. To study a
possible connection to the filament gas, we use the fit results of the
C18O(1-0) survey performed by Hacar et al. (2013).
All cores show similar properties along the 10 pc-long filament. N2D+(2-1)
shows the most centrally concentrated structure, followed by N2H+(1-0) and
DCO+(2-1), which show similar spatial extent, and H13CO+(1-0). The non-thermal
contribution to the velocity dispersion increases from higher to lower density
tracers. The change of magnitude and direction of the total velocity gradients
depending on the tracer used indicates that internal motions change at
different depths within the cloud. N2D+ and N2H+ show smaller gradients than
the lower density tracers DCO+ and H13CO+, implying a loss of specific angular
momentum at small scales. At the level of cloud-core transition, the core's
external envelope traced by DCO+ and H13CO+ is spinning up, consistent with
conservation of angular momentum during core contraction. C18O traces the more
extended cloud material whose kinematics is not affected by the presence of
dense cores. The decrease in specific angular momentum towards the centres of
the cores shows the importance of local magnetic fields to the small scale
dynamics of the cores. The random distributions of angles between the total
velocity gradient and large scale magnetic field suggests that the magnetic
fields may become important only in the high density gas within dense cores.Comment: Accepted for publication in A&A. The abstract is shortene
Tailoring correlations of the local density of states in disordered photonic materials
We present experimental evidence for the different mechanisms driving the
fluctuations of the local density of states (LDOS) in disordered photonic
systems. We establish a clear link between the microscopic structure of the
material and the frequency correlation function of LDOS accessed by a
near-field hyperspectral imaging technique. We show, in particular, that short-
and long-range frequency correlations of LDOS are controlled by different
physical processes (multiple or single scattering processes, respectively) that
can be---to some extent---manipulated independently. We also demonstrate that
the single scattering contribution to LDOS fluctuations is sensitive to
subwavelength features of the material and, in particular, to the correlation
length of its dielectric function. Our work paves a way towards a complete
control of statistical properties of disordered photonic systems, allowing for
designing materials with predefined correlations of LDOS.Comment: 5+9 pages, 5+6 figures. Fixed confusion of references between the
main text and the supplemental material in version
Modeling of Immunosenescence and Risk of Death from Respiratory Infections: Evaluation of the Role of Antigenic Load and Population Heterogeneity
It is well known that efficacy of immune functions declines with age. It results in an increase of severity and duration of respiratory infections and also in dramatic growth of risk of death due to these diseases after age 65. The goal of this work is to describe and investigate the mechanism underlying the age pattern of the mortality rate caused by infectious diseases and to determine the cause-specific hazard rate as a function of immune system characteristics. For these purposes we develop a three-compartment model explaining observed risk-of-death. The model incorporates up-to-date knowledge about cellular mechanisms of aging, disease dynamics, population heterogeneity in resistance to infections, and intrinsic aging rate. The results of modeling show that the age-trajectory of mortality caused by respiratory infections may be explained by the value of antigenic load, frequency of infections and the rate of aging of the stem cell population (i.e. the population of T-lymphocyte progenitor cells). The deceleration of infection-induced mortality at advanced age can be explained by selection of individuals with a slower rate of stem cell aging. Parameter estimates derived from fitting mortality data indicate that infection burden was monotonically decreasing during the twentieth century, and changes in total antigenic load were gender-specific: it experienced periodic fluctuations in males and increased approximately two-fold in females
The chemical structure of the very young starless core L1521E
L1521E is a dense starless core in Taurus that was found to have relatively
low molecular depletion by earlier studies, thus suggesting a recent formation.
We aim to characterize the chemical structure of L1521E and compare it to the
more evolved L1544 pre-stellar core. We have obtained 2.52.5
arcminute maps toward L1521E using the IRAM-30m telescope in transitions of
various species. We derived abundances for the species and compared them to
those obtained toward L1544. We estimated CO depletion factors. Similarly to
L1544, -CH and CHOH peak at different positions. Most species
peak toward the -CH peak. The CO depletion factor derived toward the
dust peak is 4.31.6, which is about a factor of three lower
than that toward L1544. The abundances of sulfur-bearing molecules are higher
toward L1521E than toward L1544 by factors of 2-20. The abundance of
methanol is similar toward the two cores. The higher abundances of
sulfur-bearing species toward L1521E than toward L1544 suggest that significant
sulfur depletion takes place during the dynamical evolution of dense cores,
from the starless to pre-stellar stage. The CO depletion factor measured toward
L1521E suggests that CO is more depleted than previously found. Similar
CHOH abundances between L1521E and L1544 hint that methanol is forming at
specific physical conditions in Taurus, characterized by densities of a few
10 cm and (H)10 cm, when CO
starts to catastrophically freeze-out, while water can still be significantly
photodissociated, so that the surfaces of dust grains become rich in solid CO
and CHOH, as already found toward L1544. Methanol can thus provide
selective crucial information about the transition region between dense cores
and the surrounding parent cloud.Comment: Accepted for publication in A&A, abstract abridge
First sample of nitrogen isotopic ratio measurements in low-mass protostars
Context. The nitrogen isotopic ratio is considered an important diagnostic
tool of the star formation process, and is particularly important
because it is directly linked to molecular nitrogen . However, theoretical
models still lack to provide an exhaustive explanation for the observed
values.
Aims. Recent theoretical works suggest that the behaviour is
dominated by two competing reactions that destroy : dissociative
recombination and reaction with CO. When CO is depleted from the gas phase, if
recombination rate is lower with respect to the one, the
rarer isotopologue is destroyed faster. This implies that the isotopic
ratio in protostars should be lower than the one in prestellar cores, and
consistent with the elemental value of ~440. We aim to test this hypothesis,
producing the first sample of measurements in low mass
protostars.
Methods. We observe the and lowest rotational
transition towards six young stellar objects in Perseus and Taurus molecular
clouds. We model the spectra with a custom python code using a constant
approach to fit the observations. We discuss in appendix the validity
of this hypothesis. The derived column densities are used to compute the
nitrogen isotopic ratio.
Results. Our analysis yields an average of in the protostellar sample. This is consistent with the protosolar
value of 440, and significantly lower than the average value previously
obtained in a sample of prestellar objects. Conclusions. Our results are in
agreement with the hypothesis that, when CO is depleted from the gas-phase,
dissociative recombinations with free electrons destroy faster
than , leading to high isotopic ratios in prestellar cores, where CO is
frozen on dust grains.Comment: Accepted on A&A on 09 Oct 202
N2H+(1-0) survey of massive molecular cloud cores
We present the results of N2H+(1-0) observations of 35 dense molecular cloud
cores from the northern and southern hemispheres where massive stars and star
clusters are formed. Line emission has been detected in 33 sources, for 28
sources detailed maps have been obtained. The optical depth of (23-12)
component toward peak intensity positions of 10 sources is ~ 0.2-1. In total,
47 clumps have been revealed in 26 sources. Integrated intensity maps with
aspect ratios < 2 have been fitted with a power-law radial distribution
convolved with the telescope beam. Mean power-law index is close to
unity corresponding to the density profile provided N2H+
excitation conditions do not vary inside these regions. Line widths of the
cores either decrease or stay constant with distance from the center. The ratio
of rotational to gravitational energy is too low for rotation to play a
significant role in the dynamics of the cores. A correlation between mean line
widths and sizes of clumps has been found.Comment: 17 pages, Late
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